/Engine/Source/Runtime/Slate/Public/Framework/Application/SlateApplication.h
Sets focus for all users to theSWidgetpassed in.
void SetAllUserFocus ( const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > & WidgetToFocus, EFocusCause ReasonFocusIsChanging )